1. Technical Field
The present invention relates to an optical device, an optical device manufacturing method, and an image display apparatus.
2. Related Art
Projectors and head-mounted displays are known as projection type image display apparatuses in which images are generated by controlling the wavelength or intensity of light for each pixel in image forming elements including two-dimensionally arrayed pixels and the images are expanded and displayed by optical systems such as lenses. Liquid crystal elements or organic EL elements are used as the image forming elements and the resolutions of these elements are designed to be improved every year.
At present, in markets of image display apparatuses, products with resolutions called full high-visions have been spread. In future, these products are expected to migrate to, for example, products with high resolutions called 4K or 8 K (super high-visions).
As one of the methods of realizing such high-resolution display, there is a method of using a pixel shift device (pixel shifter) shifting a projection position of an image generated by an image forming element. As the pixel shift device, a device shifting an optical path using refraction (optical modulation) in an optical element is known.
For example, JP-A-2011-158589 discloses an optical path control device including a glass serving as an optical path changing plate that transmits an image light and changes an optical path according to an incident angle, a planar holding member that holds the glass, an opening that is provided in the holding member, a coil that is mounted along the opening, a driving circuit that electrifies the coil, a permanent magnet and a yoke that generate a magnetic field to generate a Lorentz force in the coil, and a flat spring that fixes the holding member to a support table. In such an optical path control device, an angle of the holding member and the glass with respect to light projected to the glass can be changed by changing the direction of a current flowing in the coil. By changing the angle of the glass in this way, it is possible to change the optical path of the light transmitted through the glass.
In JP-A-2011-158589, however, the detailed description of how the glass is held has been not admitted.
The glass and the holding member are considered to be stuck using an adhesive. However, depending on the adhering method, it is difficult to fill a space between the glass and the holding member with the adhesive, and there is a concern of a layer of the adhesive with a sufficient thickness being not formed between the glass and the holding member. In this case, when a temperature changes in a pixel shift device, a problem may arise in that the adhesive cracks or the glass peels.